FreedomWorks, a national organization aligned with the tea party, took its second shot at Sen. John Cornyn, R-Texas, this summer as part of a digital advertisement campaign targeting several GOP senators.

"Now some are getting cold feet," FreedomWorks continued. "Senator John Cornyn – one of the original supporters – has bowed to the Republican Establishment and no longer wishes to help Senator Lee. Why is Senator Cornyn withdrawing his support for Mike Lee?"

This marks the second noteworthy flare-up between Cornyn and FreedomWorks in recent months.

In July, Cornyn hired FreedomWorks' former campaigns director, Brendan Steinhauser, as his re-election campaign manager, describing him as the operative who "led the group's effort to elect Ted Cruz to the Senate in 2012" in a news release.

FreedomWorks responded with a statement that said Steinhauser "did not lead our efforts to elect Ted Cruz."

The most recent anti-Cornyn advertisement is part of a broader FreedomWorks campaign boosting Lee's effort in 50 states, according to group spokeswoman Jackie Bodnar. "In terms of negative ads, we have named Toomey, Heller, Cornyn and Burr specifically so far," she wrote in an email.

"The letter that you're referring to that Mike Lee authored is about a tactic, not a goal. ... I don't believe this is a particular tactic that will work," Cornyn said. "This is a disagreement among friends."

But tea party groups such as FreedomWorks and others remain emboldened in Texas, where Cruz's 2012 Senate victory shocked the Texas Republican old guard. However, a serious tea party challenger for Cornyn has yet to emerge.

Meanwhile, the window narrows to recruit a conservative rival to take on Cornyn. The filing deadline is Dec. 9 and the primary is early — March 4. A Cornyn challenger would need millions of dollars to compete in one of the most expensive and expansive media markets in the country.

A spokesman for Cornyn noted that despite FreedomWorks' current efforts, the Texas Republican ranks well with the group.

"He’s been fighting Obamacare tooth and nail for the better part of four years, which the folks at FreedomWorks have recognized by giving him a 92 percent rating and ‘Principled’ status," Cornyn spokesman Drew Brandewie said.